Straight Thru UTP Cables

We will be mainly focussing on the wiring of CAT5 cables here because they are the most popluar cables around ! You will find info on wiring the classic CAT1 phone cables as well. It is very important you know how exactly to wire UTP cables because it's the base of a solid network and will help you avoid hours of frustration and troubleshooting if you do it right the first time :) On the other hand, if you are dealing with a poorly cabled network, then you will be able to find the problem and fix it more efficiently.

Wiring the UTP cables !

We are now going to look at how UTP cables are wired. There are 2 popular wiring schemes that most people use today: the T-568A and T-568B, that differ only in which color coded pairs are connected - pair 2 and 3 are reversed. Both work equally well, as long as you don't mix them! If you always use only one version, you're OK, but if you mix A and B in a cable run, you will get crossed pairs!

UTP cables are terminated with standard connectors, jacks and punchdowns. The jack/plug is often referred to as an "RJ-45", but that is really a telco designation for the "modular 8 pin connector" terminated with a USOC pinout used for telephones. The male connector on the end of a patchcord is called a "plug" and the receptacle on the wall outlet is a "jack."

As I've already mentioned, UTP has 4 twisted pairs of wires, we'll now look at the pairs to see what colour codes they have :

As you can see in the picture on the left, the 4 pairs are labeled. Pairs 2 & 3 are used for normal 10/100Mbit networks, while Pairs 1 & 4 are reserved. In Gigabit Ethernet, all 4 pairs are used.

CAT5 cable is the most common type of UTP around the world ! It's flexible, easy to install and very reliable when wired properly :)
The left and center pictures show the end of a CAT5 cable with an RJ-45 connector; used by all cables to connect to a hub or to your computer's network card. The picture to the right shows a stripped CAT5 cable, indicating the 4 twisted pairs. And to be a bit fancy, don't think that UTP CAT5 cable only comes in one boring colour... those days are over ! You get a wide range of choices today :

Pin Number Designations for T568B

Note that the odd pin numbers are always the white with stripe color (1,3,5,7). The wires connect to RJ-45 8-pin connectors as shown below:



Color Codes for T568B
Pin color - pair name
1 white/orange (pair 2) TxData +
2 orange (pair 2) ........ TxData -
3 white/green (pair 3) ..RecvData+
4 blue (pair 1)
5 white/blue (pair 1)
6 green (pair 3) ...........RecvData-
7 white/brown (pair 4)
8 brown (pair 4)

 

Reference: http://www.firewall.cx/cabling_straight.php